Dyeing of cellulosic textile



Patented Mar. 11, 1941 UNITED STATES prams OF CELLULOSIC TEXTILE MATERIALS Ernest Edward Tallis,

Coventry, England, as-

signor to Courtaulds, Limited, London, England, a British company No Drawing. Application November 19, 1938, Se-

rial No. 241,460. In Great Britain November 4 Claims.

This invention relates to the dyeing of cellulosic textile materials.

It is well known that it is not ordinarily possible to dye cellulosic materials such as cotton, rayon, linen or the like with acid dyestuffs such as are commonly used for the dyeing of wool and the like animal fibres.

It is also known, however, that such cellulosic fibres can be dyed by acid dyestuffs ii the fibres have been pretreated with various materials. For example it has been proposed to dye such cellulosic fibres after treatment with nitrogenous materials, such as amines and ammonium bases. Treatment with solutions containing urea or thiourea mixed with or precondensed with aldehyde followed by heating to obtain condensation products on the fibres has also been proposed for this purpose. It has also been stated that the methylol compounds of urea or thiourea do not possess sufllcient chemical aflinity for acid dyes to be useful technically for dyeing purposes. In view of this a proposal has been made to use the initial condensation products of formaldehyde with dicyandiamide, guanidine or heat-treated urea, which while not detrimental to the good textile properties of the fibre lend it a pronounced amnity for acid dyestufis and in some cases for basic dyestuffs.

In British Patent No. 319,822 a process of manui'acturing new compounds by the interaction of cyanamide with formaldehyde is described and it is stated that the properties of the product obtained by condensing under acid conditions are different from those of the product obtained by condensing under alkaline conditions.

According to the present invention the process for improving the dyeing properties of cellulosic textile materials, comprises incorporating in the said materials a product obtained by causing cyanamlde and formaldehyde to react under acid or neutral conditions.

One method oi carrying out the said process, comprises impregnating the said cellulosic textile materials with a solution, obtained by mixing in the cold solutions of cyanamide and formaldehyde, which solution is maintained slightly acid. The best results are obtained when the pH value of the solution lies between 5.0 and 6.5. After impregnation the material is dried and heated to ensure reaction between the cyanamide and formaldehyde. The cyanamide and formaldehyde may be partially or wholly precondensed by heating the mixed solution at raised temperatures, for example to centrigrade, under slightly acid conditions, preferably at a pH value of 5.0. The material after impregnation with the solution thus obtained is dried and heated to complete the reaction between cyanamide and formaldehyde in the material.

Alternatively, the process according to the present invention, may be carried out by incorporating in the cellulosic solution, for example, viscose, which is to be used for forming cellulosic threads, the product which is precipitated on prolonged heating above 60 centigrade of a solution'of the initially slightly acid. solution obtained by mixing solutions of cyanamide and formaldehyde.

An intensifier or any other useful compound, for example ammonium thiocyenate, which greatly increases the affinity of the textile material ior certain direct dyestuffs may be added to the solutions used for the treatment of such materials. If these lntensifiers or other compounds are of a basic nature, for example,triethylamine, then it is necessary to neutralise them before they are incorporated in the treating solution.

The cellulosic materials obtained according to the present invention have an increased afilnity for many classes of dyestuffs which may be applied to such materials, including direct cotton, sulphur, vat, azolc, basic and acid dyestuils, and also those dyestufi's specially evolved for the dyeing of cellulose acetate or the like cellulose derivatives. Moreover, the fastness to washing processes of the resulting dyed material is greatly improved.

The following examples illustrate methods of carrying the present invention into effect, although the invention is not restricted to these examples.

Example 1 12 parts of crude calcium cyanamide are extracted with 36 parts of water at from 35 to 45 centigrade for 30 minutes and subsequently filtered and neutralised with strong sulphuric acid. The calcium sulphate is filtered ofl. To the filtrate are added 15 parts of commercial formaldehyde solution (containing 40 per cent of formaldehyde), 1 part of ammonium thiocyanate and 15 parts of water. Viscose staple fibre is steeped in this solution, squeezed out and centlfuged to twice its original weight. It is then dried by known processes and finally heated for twenty minutes at centigrade. It is then dyed at the boil for one hour with l per cent oi azo-geranine 2 G. S. and 2 per cent of sulphuric acid. A rich scarlet shade is imparted to the fibre comparable with that developed by the same dyestufi on wool.

2 Example 2 A solution, containing 4 per cent of cyanamide and 8 per cent of formaldehyde, at a pH value of 5.0, is heated at 80 centigrade until a voluminous white precipitate is formed. The precipitate is filtered off, washed anddried. It is then dispersed in acetone and added to a cellulose acetate spinning solution. The cellulose acetate yarn obtained from this solution is then dyed at 80 centigrade for one hour with 2 per cent anogeranine 2 G. 8., and 2 per cent of formic acid. It can also be dyed under the same conditions with erio fast cyanine S concentrated.

Example 3 monium thiocyanate at a pH value of 0.0. The

\ impregnated yarn is then hydro-extracted, dried and heated at 150 centigrade for 5 minutes. It is then dyed a full shade with 3 per cent coomassie red P. G. 8. (Imperial Chemical Industries) and exhausts the dye bath. Theyarn obtained is also dyed a much fuller shade with indigosol blue I. B. C. than yarn which has not been so treated.

Example 4 5 parts of a per cent solution of cyanamide are added to 0 parts of 40 per cent formaldehyde solution and the resulting solution is heated at 95' centigrade for 3 minutes. After rapidly cooling to room temperature the solution is diluted with parts of water and the solution so obtained used to impregnate staple fibre. The impregnated staple fibre is hydro-extracted and dried at centizrade the temperature then bein: raised to centigrade for one hour. The treated fibre is dyed at the boil for oi'an hour in a dyebath containing 2 per cent of arc-geranine 2 G. 8. and 2 per cent of formic acid on the weight of the fibre using a liquor to yarn ratio of 40 to 1. The dyebath is exhausted and a full shade developed on the fibre.

What I claim is:

i. A process for improving the dyeing properties of cellulosic textile materials which comprises incorporating in the said materials a product obtained by causing cyanamide and formaldehyde to react in a solution the pH value of which initially lies between 5.0 and 5.5.

2. A process asclaimed in claim 1, wherein the materials are impregnated with the solution obtained by the admixture in the cold of solutions of cyanamide and formaldehyde, which solution is maintained slightly acid at a pH value between 5.0 and 6.5, the said materials after impregnation being dried and heated to cause reaction between the cyanamide and formaldehyde.-

3. A process as claimed in claim 1, wherein the materials are impregnated with the solution obtained by heating a solution containing cyanomide and formaldehyde while maintaining the pH value of the solution between 5.0 and 0.5 to give partial or complete precondensation, and are thereafter dried and heated to complete the reaction between the cyanamide and formaldehyde.

4. A process as claimed in claim 1. wherein the product which is precipitated after the prolonged heating above 60 centigrade of a solution of cyanamide and formaldehyde the pH value of which is initially between 5.0 and 6.5, is incorporated in the cellulosic solution from which eellulosic textile threads are produced.

ERNEST EDWARD TALL-IS. 

